Term applied to watch movements and some small clock movements to indicate they have been corrected for various errors, such as isochronism, temperature, and positions.

Alloy

The mixing of more than one metal in order to produce one of greater hardness, malleability and / or durability.

Analog/Digital (Duo)

A watch that displays the time, both by hour and minute hands, (an analog display) and by digital digits (a digital display). This is also known as duo display or an AnaDigi watch. See Duo Display

Aperture

A small opening/window found on the dials of some watches in which certain indications are given, such as the hour and the date.

Auto Repeat Countdown Timer

A countdown timer that resets itself as soon as the preset time has elapsed and starts again. The countdown is repeated continuously until the stop button is pushed.

Automatic Winding Movement

An Automatic watch operates with the same principle as a mechanical manual wind watch - with the addition of a weighted pendulum called the "Rotor". The Rotor is attached to the back of the movement, and when the watch is in motion (with regular wear) the rotor spins around the inside of the watch and "automatically" winds the watch, thus eliminating the need to constantly manually wind the watch. It is important to understand that automatic watches also require a manual wind every so often. An automatic watch that has stopped or is at the end of its power reserve due to non-wear should be manually wound 30-40 times. Manually winding an automatic watch after the power reserve has ebbed or the watch has stopped ensures the watch is at full reserve when first worn, so as long as the watch is worn it will remain fully wound. When removed, the watch will continue working for the specified amount of time as indicated in your manual (generally 35-45 hours). View all Automatic Watches.

B

Balance Spring

A very fine spring in a mechanical watch that causes the recoil of the balance wheel. The length and adjustment of its length regulates the timekeeping. This is also known as a hairspring.

Balance Wheel

The part of a mechanical watch movement that oscillates, dividing time into equal segments. This is the regulating mechanism that controls the watch's timekeeping accuracy.

Barrel

A drum that holds the Mainspring in a mechanical watch. The size of the barrel directly affects the length of the Power Reserve. Some watches feature a Double-Barrel which allows for extra long power reserve. The toothed rim of the barrel drives the train.

Bearing

The support for a pivit or arbour. Jewelled bearings are used where there is a danger of rapid wear on the pivots of fast moving parts, such as the balance staff, and also train wheel pivots.

Bezel

A Bezel is a ring on the top side of the case around the crystal. Some (very few) are actually located beneath the crystal. The Bezel's purpose is to measure time increments. Some bezels can be turned in only one direction - uni-direction turning bezels. Other can be turned either way - bi-directional turning bezel. Yet others are fixed and cannot be turned - each has a specific use. The purpose of the rotating Bezel is to be able to begin timing an event at any given time by aligning the bezel's #12 at the beginning point. A fixed Bezel will usually feature a scale of sorts, such as the Tachymeter scale. See Uni-Directional Turning Bezel, Bi-Directional Turning Bezel, Tachymeter Scale

Bi-Directional Rotating Bezel

A bezel that can be moved both clockwise and counter-clockwise. It is used for keeping track of elapsed time. Allowing the bezel to be rotated either way gives maximum flexibility to beginning the timing.

Bracelet

The metal strap that goes around the wearer's wrist. A watch bracelet is typically made up of flexible, separate links that can be added or removed to adjust the bracelet's length.

Breguet Spring

The spiral hairspring on which the balance swings tends to bunch on opposite sides as it expands or contracts. The constant shift in their gravity disturbs the rate of balance, and Breguet solved the problem in 1795 by upraising the last coil of the spring and giving it a smaller curve. This Breguet overcoil encouraged the spring to develop concentrically, improving the rate of the watch and reducing the wear on the balance pivots.

Bridge

A part that is fixed to the main plate to form the frame of a watch movement. All other parts are mounted inside the frame.

C

Calendar

A function that indicates day of the month, and sometimes day of the week and the year.

Cambered

This refers to a domed or arched crystal

Caliber or Calibre

Since the early 18th Century, the calibre of a movement has denoted the position and size of its different components, notably the wheel train and the barrel. Today the term is generally used to refer to the movement, its origins or its maker

Cap jewel

The flat solid jewel upon which rests the pivot end. Also called the Endstone.

Case

The metal housing that contains a watch's parts. Stainless steel is most commonly used. While titanium, platinum, gold and silver are also common, they will increase the price of the watch.

Chapter ring

The circle on the dial that contains the numbers for the hours and minutes. So called because in early clocks it was a separate ring attached to the dial.

Chromium

Very hard crystalline metallic chemical element with a high resistance to corrosion, used as a plating type on some military watch cases.

Chronograph

A watch with a stopwatch function. A Chronograph both measures and displays elapsed times in addition to showing conventional time. Generally, the chronograph mechanism is driven by the movement of the watch and operated by two buttons on the edge of the case which start, stop and reset the chronograph. Usually the chronograph seconds hand is the large centre seconds with sub-dials for elapsed minutes and hours - although the exact display may vary. See Split Seconds Chronograph a.k.a. Rattrapantte, Mono (Single) Pusher Chronograph, Fly-Back Chronograph. View all Chronograph Watches.

Chronometer

A precision watch with a movement that has been rated by the official Swiss testing laboratory called the Controle Officiel Suisse des Chronometeres (aka COSC). The standard procedure involves measuring the performance of the movement at 3 different temperatures and in 5 different positions for 15 consecutive days. Mechanical movements that are accurate to -4/+6 seconds per day are awarded a chronometer certificate. Quartz movements must be accurate to +/-0.2 seconds per day, due to the fact that Quartz movements are inherently accurate and do not vary based on position and temperature. Very few brands go through the expense of certifying their Quartz movements. Breitling, however, is one company that does certify their quartz movements - the result is a highly accurate instrument. See Quartz Movement, Mechanical Movement, COSC. Learn more about mechanical wristwatches.

Complication

A watch with functions other than timekeeping. A simple complication would include various chronographs, alarm, annual calendar and GMT functions, to mention a few. A watch with high complications would be called a Grand Complication and would include a perpetual calendar, Tourbillon, minute repeater or equation of time functions, and others. A watch with any additional function is called a complicated watch.

A balance with a bi-metallic rim made of brass and steel. The diameter increases or decreases with changes in temperature.

Countdown Timer

This allows the wearer to know how much of a preset time has passed. Some Quartz versions sound a warning a few seconds before the pre-set time has elapsed.

Crown

The grooved knob on the outside of the case, used for setting the hands on a watch, and the day and date, where applicable. It is also used for winding the mainspring of a mechanical watch. The crown is also known as a winder or winding stem. See Screw-Down Crown, Winding Crown

Crystal

This is the clear cover on the watch face (dial). It may be made of glass, plastic, mineral crystal or sapphire crystal (a scratch-resistant synthetic material). Its purpose is to protect the watch face.

D

Day/Date

A watch that shows both the day of the week and the date of the month. View all Day Date Watches.

Day/Night or AM/PM Indicator

A feature that indicates whether the indicated time is AM or PM. This feature can be found mostly (although not limited to) in watches with a GMT/Dual time display or a World Time Display to help know whether it is day or night in the other time zones.

Deployment/Deployant Buckle

A buckle that attaches to either side of the strap. The buckle is expandable so that the watch can be slipped on the wrist and snaps shut on the wrist. Once set to the correct size it need not be resized, thus reducing stress to the strap and elongating its life. This buckle also offers additional security while putting on and taking off the watch.

Detent

The setting lever. A detainer or pawl.

Dial

This is the face of the watch, showing the time.

Digital Display

A watch that shows the time in numbers, or digits, rather than hands and a dial. Liquid crystal display (LCD)is commonly used.

Dual Time

A watch that shows local time and the time in at least one other time zone. This is generally displayed by an additional hour hand which tracks time in a 24 hour mode. Some watches have a separate sub-dial showing the full clock at the additional Time Zone. See GMT, World Time Display.

Duo Display

A display that shows the time both by hour and minute hands (an analogue display) and by numbers (a digital display). This is also known as AnaDigi display. See Analog/Digital Display

Duplex escapement

A watch escapement in which the escape wheel has two sets of teeth. One set locks the wheel by pressing the balance staff. The other set gives impulse to the balance. The balance receives impulse at every other vibration.

E

Ebauche

A term used by Swiss watch manufacturers to denote the raw movement without jewels, escapement, plating, engraving.

Elapsed Time Rotating Bezel

A graduated rotating bezel that is used to keep track of periods of time. The bezel can be rotated so the wearer can align the zero of the bezel with the watch's minutes or seconds hand. The elapsed time can then be read off the bezel, rather than the wearer having to perform a subtraction necessary if he used the watch's regular dial.

EOL

This is the End-Of-Life battery indication in Quartz-powered watches. Generally the seconds begin to tick once in 4 seconds indicating that the power is low and it is time to change the battery.

Engine Turning/Turned

This is a centuries-old craft that, still today, involves the use of antique machines to engrave delicate patterns on metal watch components, including cases, dials, bezels and movements. It is also known as guilloche. See Guilloche

Escapement

The device at the heart of virtually all time-keeping mechanisms. It provides the impulses to maintain the oscillations of the balance wheel or pendulum which governs the rate at which the escapement lets the wheels and hands of the watch revolve.

F

Flat hairspring

A hairspring whose spirals develop on a flat surface, as opposed to the overcoil (Breguet overspring).

Fly-back Chronograph

Retour-en-vol in French, a chronograph which restarts the instant it is brought back to zero without the need to stop, reset & restart the chronograph - it is particularly useful to pilots. Pressing the lower push-piece only, they can immediately reset the chronograph to time each successive leg of a search pattern. Without this facility they would have to use two push pieces to stop, return to zero and restart the chronograph while starting a new leg. View all Fly-back Chronographs.

Fourth wheel

Usdually the wheel which carries the second hand and drives the escape wheel. It is the fourth wheel from the great wheel in the going train of the watch.

Function

A term used to describe the various different tasks a watch can perform such as chronograph and countdown timer. These are also known as complications.

G

Gear Train

The system of gears which transmits power from the mainspring of the watch to the escapement.

German silver

A silver-white alloy composed of mainly copper, zink, nickel.

GMT Time Zone

Greenwich Mean Time (GMT) is also known as Zulu Time and UTC (Universal Time Coordinated). The standard by which all World Time is set was agreed at the 1884 International Meridian Conference at Washington DC, USA. It placed Greenwich on the Prime Meridian (Zero Longitude). Greenwich Mean Time or GMT is the time standard against which all other time zones in the world are referenced. It is the same all year round and is not affected by Summer Time or Daylight Savings Time. GMT was originally set-up to aid naval navigation when the globe started to open up with the discovery of the "New World" (America) in the fifteenth Century. Generally when the GMT term is used with watches it refers to the ability of the watch that shows local time and the time in at least one other time zone in a 24 hour mode. The reason for showing the additional time zone in 24 hour mode is to allow the wearer to know if the second time zone is in AM or PM. See Dual Time, World Time or View all GMT Time Zone Watches.

Guilloche

Guilloche/Engine Turning is an engraving technique in which a very precise intricate repetitive patterns or design is mechanically etched into an underlying material with very fine detail. Specifically, it involves a technique of engine turning, called guilloche in French, after the French engineer "Guillot", who invented a machine that could scratch fine patterns and designs on metallic surfaces. See Engine Turning

H

Hairspring

A very fine spring in a mechanical watch that causes the recoil of the balance wheel. The length and adjustment of its length regulate the watch's timekeeping. It is also known as a balance spring.

Helium Escape Valve

Professional Divers watches are designed with the needs of deep water divers in mind. These divers regularly spend extended periods of time in diving bells at pressure, breathing Hypoxic trimix or other mixed gases with helium in them. Because helium is such a small molecule (the second smallest there is), over time in a pressurized diving bell, helium will sneak its way past the o-rings into the inside of a dive watch. While at depth this causes no problem, it will as the divers decompress the helium which is unable to escape the watch. With a standard dive watch this would lead to the watch crystal popping out from internal pressure. To stop this happening, high-end, professional diver watches have a helium escape valve or helium bleed valve to let out this extra pressure during decompression. This is a one-way valve which allows the helium to escape.

Horology

The science of time measurement, encompassing the art of designing and constructing watches.

I

Index Hour Marker

A simple stick/line design hour indicator on an analog watch dial, used instead of numerals.

Isochronism

Quality of keeping equal time during the normal run of the mainspring. Usually the qualities of a well formed overcoil hairspring.

J

Jewels

Synthetic gemstones that act as bearings for the gear trains, reducing friction and wear.

L

Lever Escapement

The lever divides into two pallets which lock and unlock the escape wheel teeth. Tthe action is governed by the balance engaging the other end of the lever, the escape teeth sliding on the inclined pallets life the lever to impulse the balance.

Ligne

A Swiss watch size. 2.2558mm or 0.0888 in.

Liquid Crystal Display (LCD)

Liquid crystal display (LCD) watches show a numeric display continuously by means of the liquid held in a thin layer between two transparent plates. The numbers are made up of seven segments that form the number 8 when all are activated. They are activated by an electronic impulse.

Luminous

Luminous Hands and/or Hour Markers - is a standard feature on many watches. The hour markers and/or hands have a coating of "glow in the dark" which will illuminate in the dark so you can tell the time where there is insufficient light. Results vary by the amount and quality of luminous material used.

Lugs

The arms of the watch case that hold the strap or bracelet.

M

Main Plate

The base plate upon which all other parts of a watch movement are mounted.

Mainspring

The coiled spring which provides the power to drive a mechanical watch movement.

Manual Wind Movement

A Manual watch operates by manually winding the crown which winds the mainspring in the barrel, thus powering the watch. Once wound it will stay working for the specified amount of time as indicated in your manual (generally 35-45 hours). See Automatic Winding Movement, Quartz Movement, Winding Crown

Marine Chronometer

A highly accurate mechanical or electronic timekeeper that is enclosed in a box and is used for determining the longitude on board a ship. Marine chronometers with mechanical movements are mounted on gimbals so they are in the horizontal position that is essential for their precision.

Meantime screws

The adjustable screws in a beter grade balance used to bring the watch to close time without the use of the regulator.

Measurement Conversion

A feature that allows the wearer to convert one type of measurement into another. It usually consists of a graduated scale on the bezel or dial.

Mechanical Movement

A "Mechanical Movement" is the term for watch that runs without an outside electrical source. The watch's mechanism is composed of multiple parts, gears, screws and springs. By winding the mainspring (either manual-winding or via automatic winding) the watch will begin to operate.

View all Mechanical Watches.

Micron

This is a thousandth of a millimeter and is a measurement used for the thickness of plating..

Mono (Single) Pusher Chronograph

A stop watch operated by a single button. While 99% of chronographs are operated by the use of two button - one to start and stop the stopwatch, the second to reset the stopwatch; a Mono Pusher complication allows for 1 button to start, stop and reset the stop-watch. See Split Seconds Chronograph a.k.a. Rattrapantte, Fly-Back Chronograph

Movement

The motor of a watch that makes it keep time and perform functions. See Automatic Wind Movement, Manual Wind Movement, Quartz Movement.

N

Nato Strap

MoD-issued G10 (Nato) straps were nylon, initially only contracted in “Admiralty Grey” with a width of 20mm, and had chrome-plated brass buckle and keepers. Another key trait was a second, shorter piece of nylon strap attached to the buckle. Since the strap was to be used by the military, it needed to be functional and fail-safe. The extra nylon had a keeper at its end through which the main part of the strap passed through after it had been looped behind the watch.This created a pocket, limiting the distance the case could move. As long as the strap was passed through properly and snugly on the wrist, the case would stay exactly where it was needed. The bonus feature of a strap that passes behind the watch is that in the event a spring bar breaks or pops out, the case will still be secured by the other spring bar.

A balance and spring composed of alloys that will not retain magnetism after being put through a magnetic field.

Numerals

Numeral (Roman and Arabic) are used to present information in the dial and sub dials

P

Pin pallet

The lever escapement wherin the pallet has upright pins instead of horizontally set jewels.

Power Reserve Indicator

An indication of the state of wind in the main spring. A hand on the dial points to the number of hours the movement will work before it runs down. Also known as Reserve de Marche. View all Watches with Power Reserve Indicators.

Push-Piece

A button that is pressed to work a watch function such as a chronograph, alarm or date corrector.

Q

Quartz Crystal

Quartz is a piezoelectric material, meaning that it generates an electrical charge when mechanical pressure is applied. These crystals also vibrate when a voltage from an outside source, such as a battery, is applied. Piezoelectricity was discovered by Pierre Curie and his brother Jacques in 1880. In the early 1920's, W.G. Cady recognized that due to their elastic qualities, mechanical strength and durability, quartz crystals could be used to fabricate very stable resonators. Cady also concluded that the crystal could be cut in specific ways which would create resonators of almost any frequency that were practically independent of temperature variations. Quartz crystals were first used as a time standard by Warren Marrison, who invented the first quartz clock in 1927. Juergen Staudte invented a method for mass-producing quartz crystals for watches in the early 1970s.

Quartz Movement

This is an electronic watch movement with a quartz crystal that oscillates when a current is applied to it. The power to run the watch is normally provided by a battery or a capacitor. A quartz movement is generally more accurate than a mechanical movement. View all Quartz Watches.

R

Radium

Radium dials are watch, clock and other instrument dials painted with radioluminescent paint containing radium-226. The 1900s (decade) were the peak of radium dial production, as radiation poisoning was then unknown; subsequently, radium dials have largely been replaced by phosphorescent- or occasionally tritium-based light sources.

Rattrapante/Split Seconds Chronograph

See Split Seconds Chronograph

Regulator or Regulateur

A Regulator display separates the minute and hour hands onto a separate axial and sub-dial. This allows for accurate time telling at a glance without the chance of having the watch hands covering each other. View all Watches with Regulator Displays.

Reserve de Marche

See Power Reserve Indicator

Retrograde

A watch with a retrograde display does not display the function in a circular fashion, as we are used to seeing. Rather, it sets out the functions in a linear manner. Instead of the hands going round in a circle, they travel along an arc, and when they get to the end, they jump back to the beginning. View all Retrograde Watches.

Rotating Bezel

A bezel around the watch that can be rotated. It has various timekeeping functions

Rotor

This is the oscillating part of an automatic watch that winds the mainspring.

S

Sapphire Crystal

Sapphire crystal is a very hard transparent material commonly used for "scratch-proof" watch glasses. Made by crystallizing aluminum oxide at very high temperatures, it is chemically the same as natural sapphire and ruby, but without the small amounts of other elements such as iron, titanium or chromium that give the gemstones their colors. Sapphire (whether natural or synthetic) is one of the hardest substances, measuring 9 on the Mohs scale, a system for rating the relative scratch hardness of materials. (Diamond measures 10, the highest rating, and the hardest steels are 8).

Screw-Down Crown

Where the crown is threaded and tightens to the case by screwing the crown into a matching threaded tube that is part of the case. The crown has a gasket that is compressed and seals the opening when the crown is tightened - thus ensuring water resistance. A Screw-Down Crown is an essential feature for any watch you intend on swimming with. An additional benefit of the Screw-Down Crown is that the crown is somewhat more protected from accidental knocks. See Winding Crown, Crown

Second Time Zone Indicator

An additional dial that can be set to the time in another time zone. This allows the wearer to know the time in two zones simultaneously. See GMT Time, Dual Time, World Time

Shock Absorber

A resilient bearing which takes up the shocks received by the watch's balance staff and protects its pivots from damage.

Slide Rule/Navigation Computer

A device consisting of a scale on the outer edge of a watch face which enables mathematical calculations such as fuel consumption, climbing times and converting miles into nautical miles or kilometers

Solar Powered Batteries

Batteries in a quartz watch that are recharged via solar panels on the watch face.

Split-Seconds Chronograph/Rattrapante

A Chronograph with two centre seconds hands, the extra hand runs concurrently with the main chronograph hand but can be stopped independently then made to catch up with the running chronograph. Thus called the "Split Seconds hand" which refers to two hands - a flyback (Rattrapante) hand and a regular chronograph hand. Both hands move together with the ability to time laps or multiple finishing times, the wearer can stop the flyback hand while the chronograph hand continues. This, in effect, splits the hand in two. The split seconds thus allows recording the successive or additional times of events that start together. View all Split-Seconds Chronographs and Rattrapante watches

Staff

A pivoted arbour or axle usually referred to the axle of the balance (balance staff)

Stainless Steel

A durable metal alloy that is almost rust resistant and rarely corrodes or discolors and, therefore, is highly suitable for watch case and bracelets. It is sometimes used on the case backs of watches made of other metals.

Stopwatch

See Chronograph

Stepping Motor

The part of a quartz analogue movement that moves the gear train and in turn moves the watch's hands.

Silver

Silver is a eflective precious metal, which is 92.5% pure and is often used in watches and watch dials.

Subsidiary Dial

A small sub-dial on a watch face used for purposes such as indicating the date, power reserve or keeping track of elapsed time.

Swiss-Made

A watch may only bear the Swiss-Made label if the assembly work of the movement and watch was started, adjusted and controlled by the manufacturer in Switzerland. Furthermore, the law requires that at least 50% of the components of the movement be manufactured in Switzerland. The case and bracelet must not be manufacturered in Switzerland, however the parts must be delivered to Switzerland unassemebled and be assembled in Switzerland.

Swiss A.O.S.C.

A certificate of origin - a mark that identifies that a watch has been assembled in Switzerland and has components of Swiss origin.

T

Tachymeter Scale/Tachometer

Common feature in chronograph watches. Measures the speed over a predefined distance. The wearer starts the chronograph when passing the starting point and stops it when passing the finish. The wearer can read the speed in units per hour off the tachometer scale. The scale is generally engraved on the bezel or printed on the outer diameter of the dial.

Tang Buckle

A tang buckle is a traditional Loop and Pin (belt type) buckle.

Tank Watch

A rectangular watch with bars along the sides of its face. It was inspired by the tracks of tank used in World War II and designed by Louis Cartier..

Timer

A device for registering intervals of time with out any indication of the time of day.

Titanium

A metal with a slightly darker/greyer appearance than Stainless Steel. Titanium is stronger and lighter than steel. Titanium is used increasingly in watch making, especially for sports and divers watches as it is resistant to salt water corrosion. View all Titanium Watches.

Totaliser

A mechanism that keeps track of and displays elapsed time, often on a subsidiary dial.

Tritium

Tritium is used as a radioactive tracer, in radioluminescent light sources for watches and instruments, and in nuclear weapons.

U

Uni-Directional Rotating Bezel

A bezel that can be rotated in one direction only and is used to monitor elapsed time. A ratchet mechanism is often in place to prevent it rotating in the other direction. It is often found on divers watches to prevent the diver from running out of air by overestimating remaining air supply if the bezel is accidentally moved from the original position. The fact that the bezel moves in one direction only is a fail-safe feature which means the diver can only underestimate remaining air supply.

Up and Down indicator

The indicator hand or window indicator that tells how much the mainspring has been unwound.

V

Vibration Per Hour or VPH

This refers to the movement of an oscillating element that is limited by two extreme positions. The balance of a mechanical watch usually vibrates at a rate of five or six a second, more commonly recognized by (but not limited to) 36,000 28,800 or 18,000 vph

W

Water Resistance

A watch that is water resistant can withstand water to a certain extent. Check the watch manual to find out the exact level of water resistance your watch is. The "Water Resistant" feature is common on most watches. It is important to remember that the water resistant rating is granted when the watch is new and tested in ideal conditions. As the watch ages the seals and gaskets begin to erode these ratings decline. Therefore it is necessary to have the water resistance tested every year. Learn more about water resistance.

Winding

This is the action of tightening the mainspring of a watch. It can be done manually, by means of the crown, or automatically, via a rotor which is made to swing by the movement of the wearer's wrist.

Winding Stem/Winding Crown

The grooved button on the outside of the case, used for setting the hands of the watch and the day and date of where applicable. It is also used for winding the mainspring of a mechanical watch. It is also known as the crown. See Crown